Existing Phase Diagrams Research Articles

Evolution of Jupiter and Saturn with helium rain

The phase separation between hydrogen and helium at high pressures and temperatures leads to the rainout of helium in the deep interiors of Jupiter and Saturn. This process, also known as “helium rain”, affects their long-term evolution. Modeling the evolution and internal structure of Jupiter and Saturn (and giant exoplanets) relies on the phase diagram of hydrogen and helium. In this work, we simulated the evolution of Jupiter and Saturn with helium rain by applying different phase diagrams of hydrogen and helium and we searched for models that reproduce the measured atmospheric helium abundance in the present day. We find that a consistency between Jupiter’s evolution and the Galileo measurement of its atmospheric helium abundance can only be achieved if a shift in temperature is applied to the existing phase diagrams (−1250 K, +350 K or −3850 K depending on the applied phase diagram). Next, we used the shifted phase diagrams to model Saturn’s evolution and we found consistent solutions for both planets. We confirm that de-mixing in Jupiter is modest, whereas in Saturn, the process of helium rain is significant. We find that Saturn has a large helium gradient and a helium ocean. Saturn’s atmospheric helium mass fraction is estimated to be between 0.13 and 0.16. We also investigated how the applied hydrogen-helium equation of state and the atmospheric model affect the planetary evolution, finding that the predicted cooling times can change by several hundred million years. Constraining the level of super-adiabaticity in the helium gradient formed in Jupiter and Saturn remains challenging and should be investigated in detail in future research. We conclude that further explorations of the immiscibility between hydrogen and helium are valuable as this knowledge directly affects the evolution and current structure of Jupiter and Saturn. Finally, we argue that measuring Saturn’s atmospheric helium content is crucial for constraining Saturn’s evolution as well as the hydrogen-helium phase diagram.

Thermodynamic Assessment of the NaCl-CrCl2, NaCl-CrCl3, and FeCl2-CrCl2 Pseudo-Binary Systems for Describing the Corrosion Chemistry Between Molten Salt Fuel and Steel

A thorough understanding of the corrosion chemistry between molten salt fuel and structural materials (e.g., steel) is key for the advancement of Molten Salt Reactor technology. In this work, we consider more specifically the case of a chloride fuel salt mixture and the thermochemistry of a salt mixture such as (NaCl-MgCl2-PuCl3) in interaction with (Fe, Cr, Ni). The present work aims at the development of a thermodynamic model of the key subsystems NaCl-CrCl2, NaCl-CrCl3, and FeCl2-CrCl2 to predict corrosion products that may form between molten salt and structural materials. The Modified Quasichemical Model in the quadruplet approximation is used to describe the Gibbs energy of the liquid phase. A critical review of the existing phase diagram and thermodynamic data on theses systems is first presented. To alleviate the lack of data, ab initio calculations coupled with a quasi-harmonic approach are performed to estimate the thermodynamic properties for the intermediate solid compounds Na2CrCl4 and Na3CrCl6, which exist in the NaCl-CrCl2 and NaCl-CrCl3 systems, respectively. These atomistic simulation data together with selected experimental data are then used as input for the thermodynamic assessment of the three subsystems.

Comprehensive understanding on phosphorus precipitation in heavily phosphorus-doped Czochralski silicon

Heavily phosphorus-doped Czochralski (HP-CZ) silicon is an important substrate material for manufacturing power electronic devices. The high concentration of phosphorus impurities may be supersaturated during the crystal growth of HP-CZ silicon or device manufacturing. Thus, understanding phosphorus precipitation in HP-CZ silicon is of technological significance. Herein, a panoramic view of phosphorus precipitation in HP-CZ silicon is presented in terms of crystallography, thermodynamics, and kinetics. It is found that the orthorhombic SiP precipitates can form during the crystal growth of HP-CZ silicon and also during the post-anneals of HP-CZ silicon at 450–1050 °C. Along with increasing annealing temperature, the formed SiP precipitates tend to adopt the platelet, polyhedron, and sphere-like shapes. Moreover, the excess point defects, i.e., silicon self-interstitials and vacancies, are found to affect phosphorus precipitation occurring in the low and high temperature regimes in different ways. In light of the kinetics of phosphorus precipitation at different temperatures, it is deduced that phosphorus precipitation follows a growth law in compliant with Ham's theory to a large extent. As an important output of this work, the temperature-dependent phosphorus solubilities in the dislocation-free silicon, which have been hardly acquired previously, are derived on the basis of investigating phosphorus precipitation in a set of HP-CZ silicon wafers with different phosphorus concentrations. Moreover, the derived solvus line for the phosphorus impurities in silicon could be a beneficial supplement to the existing phase diagram of the Si–P binary system in the extremely silicon-rich corner.

Experimental investigation and thermodynamic re-assessment of the Ti–Zn system and atomic mobility of its bcc phase

Detailed thermodynamic and kinetic descriptions of the Ti–Zn system are of especial significance for designing novel titanium alloys. However, there are still inconsistencies between the literature data and the existing phase diagram of the Ti–Zn system. Besides, little report about the kinetics of the Ti–Zn system is available. In the present work, the Ti–Zn system has been revisited via experimental, ab initio and CALPHAD (CALculation of PHAse Diagrams)-type investigations with a thermodynamic database being in good agreement with experimental information. A Ti/Zn diffusion couple and a Zn-rich equilibrated alloy were employed to contribute to the knowledge of the phase equilibria at 500 °C and 600 °C. The formation enthalpies of the intermetallic Ti–Zn compounds were computed via ab initio calculations, while those of body-centered cubic (bcc) and hexagonal-close packed (hcp) phases were obtained with the special quasirandom structure (SQS) method. In addition, another diffusion couple of bcc Ti/Ti-3at.% Zn was assembled and annealed at 900 °C and 1100 °C respectively for 72h to extract interdiffusion coefficients. Based on the newly developed thermodynamic description in this work and our experimental results, the atomic mobility parameters of the bcc phase for the Ti–Zn system were assessed.

Electrochemical Investigation of (De-)Lithiation Behaviors of Al Anodes and the Solubility Range of β-Lial Phase at Room Temperature

Alloy anodes have been extensively studied over past decades to replace the graphite of lithium-ion batteries (LIBs). Most efforts are made towards those anode materials with high specific capacities such as silicon and germanium. To minimize the negative impacts of the volume expansions during Li incorporation, protective coatings or specific micro- and nanostructures have been suggested, but a commercialization on a larger scale was impeded by such preparation costly procedures. Therefore, the optimal alloy anode candidate should balance the cost, capacity and manufacturing complexity rather than solely maximize the specific capacity. Aluminum, an underappreciated anode material, possesses intrinsic properties that fulfill the criteria mentioned above. The origin of the main capacity of aluminum anode is upon the formation of the β phase (LiAl; ca. 1Ah/g). However, the (de-)alloying processes of Al remain poorly understood, especially at room temperature under which LIBs usually operate.In this study, we investigate the (de-)lithiation that occurs within the solubility range of the β phase Although this Li solubility is highlighted by multiple versions of the Li-Al phase diagrams, the solubility range at low temperatures was not specified yet due to the experimental conditions of previous phase diagram studies (> 400 °C). Various electrochemical analytic tools and methods are used to shed light on the Li solubility within the β phase. The Li solubility range of the β phase is determined to be roughly 5 at% by a potentiostatic charge counting experiment at room temperature. Moreover, the cyclic voltammetry of partially lithiated Al foils shows that the β phase can be (de-)saturated without propagating the phase front towards the α phase. If galvanostatic charge and discharge is smartly controlled by taking into consideration of the solubility range, the cycling life of β-LiAl anode can be significantly improved. Not only does this piece of work provide fundamental data for the β-LiAl phase at room temperature that complements the existing phase diagrams, but also implies that aluminum foil holds great potential as an anode material for the next generation of lithium-based batteries.

Relating the Flow Processes and Bedforms of Steady-State and Waning Density Currents

© Copyright© 2020 de Cala, Ohata, Dorrell, Naruse, Patacci, Amy, Simmons, McLelland and McCaffrey. The interaction between turbidity currents and mobile substrates can lead to the development of different types of bedforms. Although much research has been conducted on bedform development beneath open channel flows, research into bedform development beneath waning gravity currents is relatively rare. Analysis of density current-related bedform development has therefore relied upon open channel flow phase diagrams. We report on an experimental study designed to assess the development of bedforms under steady and waning saline density currents. The experimental density currents developed stepped density profiles in which a higher-density basal zone was separated from the ambient fluid by a zone of intermediate density; any bedforms that developed were contained within the bottom layer of the current. Under different conditions ripples, dunes, downstream migrating antidunes and long wavelength antidunes were observed to form and could be distinguished based on their interactions and phase relationships with the upper surface of the lower denser layer of the current. Due to limited mixing between the upper and lower layer of the current and maintenance of current momentum, currents set with slowing discharge flow rates maintained a steady flow velocity in the lower layer of the flow. As a result, sustained bedform formative conditions were achieved within this lower layer, while waning current conditions effected the rest of the flow. Under waning currents, it was seen how pre-existing bed states can determine the subsequent evolution of bedforms. This illustrates the limitations of existing phase diagrams as they do not account for trajectory or rate of passage of flows through different bedform phase spaces. In order to establish a reliable quantitative association between the flow regime and the type of bedform development, it is critical to adopt an appropriate Froude number calculation method for stratified flow. The updated density current phase diagram indicates supercritical flow can be achieved at lower flow velocities than for open channel flows due to the effects of reduced gravity. Bedform depositional structures found in outcrop and on the modern sea floor provide data that helps to interpret the hydrodynamic and sedimentological character of the current that formed them. Therefore, understanding the processes involved in bedform development beneath density currents will enable more accurate estimation of the properties of flows.

First- and second-order phase transitions in Fe-(17-19)at.%Ga alloys

The structure of the Fe-(17.5–19.5)at.%Ga alloys in as-cast and nearly equilibrium states is studied using XRD, ND, and EBSD. In disagreement with the existing phase diagrams, the long-term isothermally annealed at 450–500 °C Fe-17.5%Ga alloy has a two-phase structure with two co-existing ferromagnetic phases: bcc-originated A2(D03) as a matrix and a fcc-originated A1(L12) needle-shaped precipitates. The phase transitions during cooling of 17.5 and 19.5%Ga alloys from the A2 range of the phase diagram with different cooling rates were used to plot, at least partly, Time-Temperature-Transformation (TTT) diagrams. The critical cooling rates for starting first- and second-order transitions are determined for the Fe-19.5%Ga alloy. The effect of long-term annealing on magnetostriction is reported.

Direct Imaging of Lipid Domains in Nanoscale Vesicles by cryoEM

Direct imaging of membrane domains has provided evidence necessary to answer a wide range of scientific questions; direct imaging has been used to prove that vacuole membranes phase separate in living yeast cells and to show that current theories of modulated phases are incomplete. Many deep questions about membrane domains remain extremely challenging to answer because our current arsenal of direct imaging techniques is incomplete. For example, the existence of sub-micron domains in model membranes (and in some cases, the cell plasma membrane) has been inferred by indirect methods such as FRET, neutron scattering, and NMR. In cases where indirect methods require assumption-dependent models, it is important to verify the results directly with microscopy. To overcome current limitations, new methods of imaging sub-micron membrane domains are needed. Here, we present two novel cryo-EM methods of imaging sub-micron lipid domains in ternary model membranes. The first method employs a monovalent probe that is both fluorescent and electron-dense, enabling direct, and model-free comparisons for a single vesicle analyzed by both fluorescence microscopy and electron microscopy. The second method is entirely label-free; it identifies domains that are thicker than the surrounding membrane. To validate this method, we leverage existing phase diagrams (obtained through fluorescence microscopy) and AFM data to identify compositions with a membrane thickness difference between the Lo phase and Ld phase of ≥ 1 nm. We benchmark our techniques against known phase diagrams and demonstrate that our new methods accurately quantify the area fractions of each phase.

Liquid Regions of Lanthanum-Bearing Aluminosilicates.

The Al2O3-SiO2, La2O3-Al2O3, and La2O3-SiO2 binary phase diagrams were estimated by Redlich–Kister expression. La4.67Si3O13 (=La4.67(SiO4)3O) was introduced to improve the existing phase diagrams. The Al2O3-SiO2-La2O3 ternary phase diagram extrapolated by Kohler method was optimized. Then, the liquidus of Al2O3-SiO2-La2O3 system at 1600 °C was compared with Al2O3-SiO2-RE2O3 (RE = Rare Earth Elements) systems and experimental results in other literature. The high temperature experiments were conducted in the tube furnace at 1500 °C. Then the field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) were employed to verify the calculated liquid region and precipitates phase at 1500 °C. Moreover, the liquidus of binary systems were compared with FactSage results and experiments. The optimized ternary phase diagram shows the relatively reliable region of liquid phase, and it is significant to the seal glass of solid oxide fuel cells and other fields being related to RE containing silicates.

Microstructural characterization of the as-cast and annealed Pu-10Zr alloy

Phase diagrams constructed for the Pu-Zr binary system report the existence of θ-(Pu,Zr), δ-(Pu,Zr), γ-Pu, α-Pu, β-Pu, and ζ-Pu28Zr phases in Pu-enriched region, when Pu concentrations exceed 75 at.% (equivalent to 89 wt% Pu). The compound θ-(Pu,Zr) has been said to occur at about 20 at.% Zr, but the regions for θ-(Pu,Zr) on the Pu-rich side have not been well defined. In an effort to understand the phases formed in Pu-Zr binary alloys and define the boundary between θ-(Pu,Zr), (θ+δ), and δ-(Pu,Zr) regions, Pu-10Zr (in wt.%, equivalent 23 at.%) alloys were scrutinized in this contribution. This manuscript details microstructural characterization and phase identification results obtained using electron microscopy-based techniques for a Pu-10Zr alloy before and after annealing at 550 °C. In contradiction with predicted phase diagrams, no θ-(Pu,Zr) was detected in any of the examined specimens. The phases present in as-cast fuel included a δ-(Pu,Zr) matrix with a number of smaller, randomly distributed α-Zr, ZrO2, Zr3O, PuO, and κ-PuZr2 inclusions. Heat treatment annealed out the intermetallic κ-PuZr2 phase and resulted in formation of small δ′-Pu and β-Pu inclusions. Similar to the as-cast alloys, the matrix of the annealed alloys was consistent with δ-(Pu,Zr) phase and contained small α-Zr, ZrO2, and PuO2 inclusions. Two different microscopy-based techniques were used for phase identification, but neither identified any θ-(Pu,Zr) phase. Differential scanning calorimetry was then used to determine the phase transition temperatures and enthalpies of transition for the identified phases. While our data is similar to the existing phase diagrams, a number of discrepancies are reported that call for a careful re-examination of the Pu-Zr system. This contribution discusses different scenarios that could explain the discrepancies between obtained and historical data, and provides the most logical conclusion that could be reached based on the obtained results.

The new nano-enabled phase map of ZrO2-Al2O3

Rapid development of nanotechnology often requires verification of existing phase diagrams, which were suitable for bulk materials. This work presents a new phase map (phase diagram) for Al2O3-ZrO2 crystalline powders including the role of the nanoscale particles. Al2O3-ZrO2 composites are relevant for industry for applications demanding high hardness. The nanopowders were manufactured via co-precipitation process followed by microwave hydrothermal synthesis (MHS) at 270 °C, drying at room temperature and annealing in the temperature range 300–1500 °C. The phase composition was investigated using X-ray diffraction (XRD) and Rietveld refinement analysis. The grain size and size distribution were calculated using Rietveld refinement analysis and using transmission electron microscopy (TEM). A particular feature of the composites was the nanoisolation, separation of different phases on a nanoscale. This feature limited grain growth during annealing and permitted the phase diagram for a nano-enabled system to be determined, which turned out to be different from that of conventional composites. In particular, considerable solubility of Al3+ in ZrO2 was found for temperatures less than 1000 °C.

Microstructure and calorimetric analysis of the U[sbnd]Mn binary system

The microstructure, growth kinetics, and the high temperature phase equilibria of the UMn binary system are investigated using differential scanning calorimetry. Alloys with various compositions are prepared in a positive-pressure arc melting furnace in order to examine all possible phase changes within the system. Phase composition and morphology were analyzed using XRD, SEM and EDX. Transformation temperatures and enthalpies have been assessed pertaining to: (i) allotropic phase changes αMn → βMn → γMn →δMn, (ii) two eutectic isotherms UMn2 + βMn → L and U6Mn + UMn2 → L and (iii) melting transitions as a function of composition. The development of the two intermetallic phases U6Mn and UMn2 are observed. A faceted morphology accompanies the formation of UMn2 in a matrix of U6Mn, while grain boundary decomposition is found of UMn2 in αMn. The transformation temperatures are compared to existing phase diagrams and are slightly higher than reported in literature. Experimental observations of the allotropic transformations of αMn to βMn and βMn to γMn are in agreement with a calculated phase diagram. The eutectic composition for UMn2 and αMn is found to be 55 wt%Mn, in agreement with previously reported values, while the enthalpy of fusion associated with this eutectic point is found to be 54 ± 6.5 kJ mol−1. The enthalpies of formation for the two intermetallic phases U6Mn and UMn2 are 71 ± 8.5 kJ mol−1 and 42 ± 5 kJ mol−1 respectively.

Solidification Analysis of Mg–4Zn–xSr System to Study Phase Transformations in Mg-Rich Corner

Mg–Zn–Sr alloys are suitable for biodegradable orthopaedic implants due to excellent biocompatibility and bone regeneration effect of Sr. For Sr additions exceeding 0.2 wt%, ternary phases are observed in the microstructure contrary to binary MgxZny and Mg17Sr2 intermetallics predicted by the existing phase diagrams and corrosion and mechanical properties reduce drastically. Thermal analysis employed for Mg–4Zn–xSr alloys (0 ≤ x≤2) recorded two peaks, hitherto unreported, at temperatures of ~ 514 and 409 °C with 2 wt%, and ~ 549 and 428 °C with 1 wt% of Sr added to Mg–4Zn alloy. In conjunction with SEM–EDAX and XRD analysis, one of these phases is identified as Mg11Zn4Sr3, with second one an unknown intermetallic (IM2). Formation of Mg17Sr2 phase is suppressed in the presence of Zn, and the ternary phase is favoured beyond the solid solubility of Sr in Mg. Solidification pathway of L → α-Mg + Mg11Zn4Sr3 + unknown intermetallic (IM2) has been proposed for the ternary compositions with Sr > 0.2 wt% investigated in the current study.

Synthesis and characterization of La2-yYyCuO4 with T’-structure

Superconductivity is a phenomenon when the resistivity becomes zero below the critical temperature (Tc). The appearance of superconductivity in undoped bulk samples of T’-La1.8-xEu0.2MxCuO4 (M = Sr, Ca; x = 0.05, 0.10, 0.15) has altered the existing phase diagram in superconducting cuprates and raised big questions about the mechanism of superconductivity. Here, new materials of T’-La2-yYyCuO4 with y = 0.05, 0.10, 0.15 have been synthesized by the low-temperature synthesis method in order to grow undoped superconductors with the single phase of the T’-structure. The powder x-ray diffraction analysis was performed to identify of the crystal structure, while magnetic susceptibility measurements were carried out using a SQUID magnetometer at low temperature down to 2 K. It has been found that the T’-structure is stabilized when it was annealed at 500 – 600°C. The c-axis length decreases with increasing Yttrium-concentration. For y = 0.10, the single phase of the T’-structure was obtained by the oxidation annealing at 300°C and the succeeding reduction annealing at 500°C for 24 hours. From magnetic susceptibility measurements, it has been found that no trace superconductivity is observed in all samples, which is probably due to the remaining excess oxygen suppressing the appearance of superconductivity in the sample.

Equation of state, adiabatic sound speed, and Grüneisen coefficient of boron carbide along the principal Hugoniot to 700 GPa

A equation of state (EOS) experimental technique that enables the study of thermodynamic derivatives into the TPa regime is described and applied to boron carbide (${\mathrm{B}}_{4}\mathrm{C}$). Data presented here are principal Hugoniot sound speed measurements reported using a laser-driven shock platform, providing a means to explore the high-pressure off-Hugoniot response of opaque materials. The extended ${\mathrm{B}}_{4}\mathrm{C}$ Hugoniot suggests the presence of a high-pressure phase, as recently predicted by molecular dynamics simulations, adding to the complexity of the existing phase diagram.

Thermodynamic assessment of the Nd2O3-CaO-SiO2 ternary system

In order to enable efficient recycling of rare earth metals through high temperature processes, the phase relations in rare earth oxide containing slags need to be understood. A thermodynamic description of the CaO-SiO2-Nd2O3 ternary system and its Nd-containing binary subsystems was, therefore, constructed in this study, based on existing phase diagram and thermodynamic data. The Gibbs energy of the liquid oxides in the CaO-SiO2-Nd2O3 system was modeled using the Modified Quasichemical Model. The solid phases Ca2-2xNd2xSiO4Ox, Ca3-3xNd2xSiO5, and Ca2+10xNd8-8x(SiO4)6O2-2x were modeled with polynomial expansions of the excess Gibbs energy. The optimized phase diagram of the CaO-SiO2-Nd2O3 system is in good agreement with the experimental data.

P6] Effects of alloying elements on elastic properties of Al by first-principles calculations

Detailed thermodynamic and kinetic descriptions of the Ti–Zn system are of especial significance for designing novel titanium alloys. However, there are still inconsistencies between the literature data and the existing phase diagram of the Ti–Zn system. Besides, little report about the kinetics of the Ti–Zn system is available. In the present work, the Ti–Zn system has been revisited via experimental, ab initio and CALPHAD (CALculation of PHAse Diagrams)-type investigations with a thermodynamic database being in good agreement with experimental information. A Ti/Zn diffusion couple and a Zn-rich equilibrated alloy were employed to contribute to the knowledge of the phase equilibria at 500 °C and 600 °C. The formation enthalpies of the intermetallic Ti–Zn compounds were computed via ab initio calculations, while those of body-centered cubic (bcc) and hexagonal-close packed (hcp) phases were obtained with the special quasirandom structure (SQS) method. In addition, another diffusion couple of bcc Ti/Ti-3at.% Zn was assembled and annealed at 900 °C and 1100 °C respectively for 72h to extract interdiffusion coefficients. Based on the newly developed thermodynamic description in this work and our experimental results, the atomic mobility parameters of the bcc phase for the Ti–Zn system were assessed.

Gd5(SixGe1−x)4 system – updated phase diagram

Gd5(SixGe1−x)4 for 0.41<x<0.5 is orthorhombic and ferromagnetic at lower temperature, monoclinic and paramagnetic at higher temperature, and shows a first order magnetic-structural phase transition between the two. In this range, the magnetic moment vs. magnetic field (MH) isotherms measured just above the first order transition temperature carry information about all magnetic and structural transitions. Here, the Curie–Weiss law was applied to the paramagnetic portions of the MH isotherms which allowed identification of the second order magnetic phase transition temperature of the monoclinic phase, a region where the second order transition does not occur due to the existence of the first order transition. The calculated second order phase transition temperatures of the monoclinic phase were added to the existing phase diagram. The completed magnetic-structural phase diagram carries now all the information including the magnetic transition temperatures of both monoclinic and orthorhombic phases. It was also found that the magnetic transition temperature of the monoclinic phase and the first order transition temperature are interrelated.

Predictions on the compositions, structures, and mechanical properties of intermediate phases in binary Mg–X (X = Sn, Y, Sc, Ag) alloys

It has been paid an increasing attention on the precipitation strengthening of Mg alloys. Toward designing high strength and toughness light-weight Mg alloys, the mechanical properties of stable or metastable intermetallics should be basically known. In this work, the compositions and corresponding structures of stable or metastable precipitations in the binary Mg–X (X=Sn, Y, Sc, Ag) alloys are predicted using ab initio evolutionary algorithm. Our predictions are well consistent with the existing phase diagrams but further yield potential phases and their crystallographic informations. Furthermore, the elastic moduli of the predicted intermetallics are studied based on first-principles calculations. Besides basic structural and mechanical data, we provide that the Mg–Ag alloy exhibits the larger bulk modulus and ductility when Ag composition increases, and the Mg–Sc alloy should be a promising candidate to meet the comprehensive strength, weight, economy, and efficiency requirements. Thus from the composition to the structure, further to the mechanical property, we present a systematically theoretical program for the alloys design.

Phase equilibria of an Al0.5CrFeCoNiCu High Entropy Alloy

The phase equilibria of an Al0.5CrFeCoNiCu High Entropy Alloy has been studied following 1000h exposures at 700, 850 and 1000°C. Above 1000°C, the material comprised of two fcc solid solutions, one a multi-element phase and the other a Cu rich phase. Below 1000°C, the fcc phases persisted, but were accompanied by the formation of two intermetallic compounds. In contrast to previous reports, the L12 phase was also found to precipitate through a solvus at~850°C. The results indicated that a solid state single phase field does not exist in this material at any temperature and all of the observed phases could be rationalised with reference to existing phase diagrams. This suggests that configurational entropy does not overcome the enthalpic contribution to the Gibbs energy, which governs phase equilibria of this alloy.